Viscose rayon fibers

Synthetic fibers have been characterized by a resistance to degradation over forensically relevant timescales (Table 7.4). Nylon (polyamide), polyester, and acrylic fibers show considerable resistance to soil burial. Regenerated cellulose fibers (rayon viscose), however, share the vulnerability of natural cellulose to decomposition (Rowe 1997). However, they do show a higher degree of resistance to biodegradation compared with natural fibers or regenerated cellulose, with the exception of triacetate. 

Fiber, rayon viscose A regenerated cellulosic fiber made by treating wood pulp with caustic soda, and with carbon disulfide to form cellulose xanthate that is then dissolved in a weak caustic solution. It is from the latter that extrusion and coagulation forms the fiber. 

Plastics and Other Synthetic Products. Sulfur is used in the production of a wide range of synthetics, including cellulose acetate, cellophane, rayon, viscose products, fibers, and textiles. These uses may account for 2% of sulfur demand in developed countries. Sulfur intermediates for these manufacturing processes are equally divided between carbon disulfide and sulfuric acid. 

Uses. Manufacture of rayon viscose fibers and cellophane film solvent for lipids, sulfur, rubber, phosphorus, oils, resins, and waxes insecticide... 

Viscose or rayon A well-known inherently FR viscose fiber is Viscose FR, marketed by Lenzing. The fiber is produced by adding Sandoz 5060 (Clariant 5060)-bis(2-thio-5,5-dimethyl-l,3,2-dioxa-phosphorinyl)oxide in the spinning dope before extrusion. As this additive is phosphorus based, it is similar to other phosphorus-based FRs in terms of mode of action (condensed phase). 

Rayon. Viscose rayon, like cotton, is comprised of cellulose. In the manufacturing process, wood pulp is treated with alkali and carbon disulfide to form cellulose xanthate. Subsequently, the reaction mass is forced through a spinneret and precipitated in an acid coagulation bath as it is formed into a continuous filament. The fiber has a round striated cross-section. Rayon staple is made by breaking the continuous strands into staple-length fibers. Viscose rayon is conventionally produced in diameters varying from 9 to 43 microns. 

Rigterink JH. 1988. Rayon viscose past, present and future. In Brown CLJ, ed. Occupational health in the production of artificial organic fibers. Enka, Amhem, The Netherlands, 14-19. 

Fiber, rayon The generic term for fibers, staples, and continuous filament yarns composed of regenerated cellulose but also frequently used to describe fibers obtained from cellulose acetate or cellulose triacetate. Rayon fibers are similar in chemical structure to natural cellulose fibers (cotton) except that the synthetic fiber contains short plastic units. Most rayon is made using the viscose process. 

Camille and Henry Dreyfus developed the first commercial process to manufacture cellulose acetate in 1905 and commercialized the spinning of cellulose acetate fibers in 1924 in the United States. At that time, the only other human-made fiber was viscose rayon, which was still in its early stages of commercialization. The main textile fibers were natural fibers cotton, wool, silk, and flax. Cellulose triacetate textile fiber was commercialized later in the 1950s. The tremendous technical effort by the Dreyfus Brothers resulted in more than 300 patents describing such significant inventions as the dry-spinning process and disperse dyeing. 

Various synthetic fibers appear in clothing, upholstery, and industrial uses. They are better known by commercial names, that hide their source and composition. Quite often a blend of natural and synthetic fibers is offered. The first man-made fibers (that still are of major use) are essentially based on a modification of natural cellulose. Most common in use are rayon (viscose) and cellulose-acetate (called acetate). The oldest synthetic polymer in the textile industry is the polyamide (Nylon 6-6) developed in 1935. Currently there are many synthetic fibers, like the following ... 

The structure of the cellulose has a marked influence on the subsequent decomposition [73-77] and less crystalline materials decompose more readily and in terms of thermal decomposition can be rated viscose cord rayon > viscose continuous filament > viscose rayon fiber > Fortisan fiber > Cotton > hydrocellulose. However, hydrocellulose does not follow this rule. 

Carbon fibers can be produced from a wide variety of precursors in the range from natural materials to various thermoplastic and thermosetting precursors Materials, such as Polyacrylonitrile (PAN), mesophase pitch, petroleum, coal pitches, phenolic resins, polyvinylidene chloride (PVDC), rayon (viscose), etc. [42-43], About 90% of world s total carbon fiber productions are polyacrylonitrile (PAN)-based. To make carbon fibers from PAN precursor, PAN-based fibers are generally subjected to four pyrolysis processes, namely oxidation stabilization, carbonization and graphitiza-tion or activation they will be explained in following sections later [43]. 

Alkali cellulose n. Also called regenerated cellulose, pure cellulose obtained from wood pulp, etc., reacted with strong alkah solutions at low temperatures, and is a further step in the reaction of merceriza-tion as a fiber is called rayon, viscose. 

In the spinning of rayon fibers, the viscosity of the viscose solution must be carefully controlled. In the falling ball experiment on a viscose solution, it took a 2 mm lead ball 324 s to fall 10 cm. The density of the viscose was 1.2 g/cm. What is its viscosity ... 

The conversion of cellulosic wood pulp into a textile fiber dates to the earliest periods of synthetic fiber manufacture viscose rayon and lyocell processes are well known. However, it is stiU conceivable to improve upon... 

The principle of wet spinning is shown in Figure 17.17. Wet spinning is applied for two large-scale fiber products - viscose rayon and acrylics - and one smaller product - poly(vinyl alcohol). 

Uses LubricanL antistat for textile Industry, for aflertreatment of dyed polyester fibers preparation agent for syn. fibers, esp. viscose rayon staple and wool-type polyester... 

The cellulose molecule contains three hydroxyl groups which can react and leave the chain backbone intact. These alcohol groups can be esterified with acetic anhydride to form cellulose acetate. This polymer is spun into the fiber acetate rayon. Similarly, the alcohol groups in cellulose react with CS2 in the presence of strong base to produce cellulose xanthates. When extruded into fibers, this material is called viscose rayon, and when extruded into sheets, cellophane. In both the acetate and xanthate formation, some chain degradation also occurs, so the resulting polymer chains are shorter than those in the starting cellulose. 

Originally, the word rayon was appHed to any ceUulose-based man-made fiber, and therefore included the cellulose acetate fibers. However, the definition of rayon was clarified in 1951 and includes textiles fibers and filaments composed of regenerated cellulose and excludes acetate. In Europe the fibers are now generally known as viscose the term viscose rayon is used whenever confusion between the fiber and the cellulose xanthate solution (also called viscose) is possible. 

Its early commercial success owed much to the flammabUity disadvantages of the Chardoimet process, but competition from the viscose process led to its decline for aU but the finest filament products. The process is stiU used, most notably by Asahi in Japan where sales of artificial sHk and medical disposable fabrics provide a worthwhile income. However, its relatively high cost, associated with the cotton fiber starting point, prevented it from reaching the large scale of manufacture achieved by the viscose rayon process. 

Commencing in the late 1930s, new developments to make very strong yams allowed the viscose rayon to replace cotton as the fiber of choice for longer life pneumatic tires. The pace of this line of development increased during World War II, and by the 1960s a significant part of the production of viscose yam was for tires and industrial appHcations. 

From 1910 onward waste filament yam had been chopped into short lengths suitable for use on the machinery designed to process cotton and wool staples into spun yams. In the 1930s new plants were built specifically to supply the staple fiber markets. During World War II the production of staple matched that of filament, and by 1950, staple viscose was the most important product. The new spun-yam oudets spawned a series of viscose developments aimed at matching the characteristics of wool and cotton more closely. Viscose rayon was, after all, silk-like. Compared with wool it lacked bulk, residence, and abrasion resistance. Compared to cotton, it was weaker, tended to shrink and crease more easily, and had a rather lean, limp hand. 

---